Dual hydrofoil mechanism for sailboats



April 20, 1965 J. R. POPKIN 3,179,078

DUAL HYDROFOIL MECHANISM FOR SAILBOAI'S Filed Dec. 4, 1962 3 Sheets-Sheet 1 "IE/$550M) L. INVENTOR.

ii 3 BY fi ,47 ram/ 5 V51 April 20, 1965 J. R. POPKIN DUAL HYDROFOIL MECHANISM FOR SAILBOATS 3 Sheets-Sheet 2 Filed Dec. 4, 1962 April 1965 J. R. PoPKm 3,179,078

DUAL HYDROFOIL KECHANISI FOR SA ILBOA'IS Filed D00. 4, 1962 3 Sheets-Sheet 3 if 35 |-2 J/ Ja/m/ 'e. ane/M INVENTOR.

United States Patent 3,179,078 DUAL HYDROFOIL MECHANISM FOR SAILBGATS John R. Poplrin, Los Angeles, Calif. (RA. 19723587,

7th Avn. Co. (Inf. Div. A.P.0. 7, San Francisco,

Calif.)

Filed Dec. 4, 1962, Ser. No. 242,185 9 Claims. (Cl. 114-126) This invention relates to a hydrofoil mechanism for sailboats to resist sideways slipping motion of the sailboat due to lateral wind forces and to produce a lifting force on the sailboat to improve performance characteristics and counteract the overturning forces of the wind on the sailboat. In particular, this invention relates to a dual hydrofoil mechanismv which operates unattended to appropriately and properly position one of the hydrofoils in the water as needed for proper operation of the sailboat.

Conventionally sailboats are provided with center boards or other means which serve to resist lateral motion of the sailboat'due to the wind producing lateral forces on the sails and sailboat. The center board serves this useful and necessary purpose, but also acts as a resistance to the forward motion of the sailboat and does not produce any forces, other than merely weight, tending to prevent overturning of the sailboat. As is well known, it is advantageousto shift the center of gravity 'of the weight of the boat and its contents toward the Windward such as by positioning the occupants so' that righting force is produced to combat the overturning force caused by the wind impinging upon the sail. Conversely, a similar righting force to produce stability may be induced by using a pair of hulls, as in a catamaran, or an outrigger hull to the leeward side whereby the sailboat is at least partially supported at a lateral distance toward leeward from the center of gravity of a sailboat thereby producing a righting moment force. However, such an outrigger hull also acts as a resistance to the motion of the sailboat through the water.

The overturning force applied to a sailboat by wind impinging upon the sails and the force tending to cause lateral motion of the sailboat will depend upon numerous factors such as wind velocity, sail area, direction of movement of the sailboat with respect to the direction of the wind, etc. Thus for example, when running with the wind, i.e., the sailboat moving in the same direction as the wind, there is very little need for a center board since the overturning forces and the lateral forces are relatively nominal. Although certain smaller sailboats have center boards which are removable or retractable for conditions where they are not needed, there are no conventional sailboats that are provided with a center board or center boards that can be adjusted to produce righting forces and forces resisting lateral movement which are proportional to the overturning and lateral movement forces produced by the wind.

It is well known that a properly shaped hydrofoil can cause resultant forces in a lateral direction as the hydro foil passes through the water. If such a hydrofoil were properly positioned and moved for various conditions the hydrofoil could produce the necessary forces to prevent lateral movement of the sailboat and overturning of the sailboat. Moreover, a hydrofoil offers very little resistance to passage through the water as compared to a hull and can serve to stabilize the forward motion. However, to be practical, the positioning of such a hydrofoil must be essentially automatic in response to the various force conditions encountered so that erroneous positioning of the hydrofoil by an operator does not result in overturning of the sail boat or unsatisfactory handling conditions.

Accordingly, it is a principal object of this invention to provide a novel form of hydrofoil mechanism for a sailboat that will function automatically in response to wind conditions for improving the operating characteristics of the sailboat.

, Another object of this invention is to provide a dual uydrofoil mechanism for sailboats employing asymmetrical hydrofoils wherein only one of the twohydrofoils is positioned in the water at one time and the asymmetrical shape of that hydrofoil produces forces tending to resist lateral slipping and overturning of the sailboat.

A further object of this invention is to provide a hydrofoil mechanism for sailboats whereina hydrofoil is positioned on either side of the center line of the boat at a substantial distance from the center line, and only the leeward side hydrofoil is positioned in the water during normal operation.

Still another object of this invention is to provide a hydrofoil mechanism for sailboats wherein an asymmetrically shaped hydrofoil is automatically positioned in the water at an appropriate angle in response to the lateral forces on the sailboat whereby the hydrofoil produces appropriate resistive lateral forces and lifting forces to improve the operational characteristics and stability of.

the sailboat.

A still further object of this invention is to provide a dual hydrofoil mechanism wherein the positions of the two hydrofoils are synchronized and the operational position of each is resiliently resisted in response to particular force conditions imposed upon the sailboat.

A further and more detailed object of this invention is to provide a novel form of dual hydrofoil mechanism particularly adaptable to a trimaran sailboat wherein a hydrofoil is pivotally mounted on each of the outriggers and the leeward side hydrofoil only is positioned in the water at any one time with its angular position automatically adjusted by resilient means to continually maintain the most ideal position for the particular conditions at that moment. Moreover, it is an object of this invention to provide asymmetrically shaped hydrofoils for such mechanisms whereby the leeward side hydrofoil provides a lifting force so that the outrigger may function as a planing surface rather than a merely buoyant supporting member.

Further and more detailed objects and advantages of this invention will appear from the following description and the accompanying drawings.

In the drawings: 7

FlGURE 1 is a plan view of a trimaran sailboat employing a particular preferred embodiment of the dual hydrofoil mechanism of this invention with the sails, mast and boom removed forclarity of illustration.

FIGURE 2 is an elevation of the trimaran of FIGURE 1 with the sails and masts partially broken away.

FIGURE 3 is a sectional elevation of the mechanism of this invention taken substantially on the line 33 as shown in FIGURE 2 with the hydrofoils in a different position than shown in FIGURE 2. I

FIGURE 4 is a fragmentary sectional elevation of the torsion bar mechanism used in this preferred embodimnt taken substantially on the line 4--4 as shown in FIGURE 3.

FIGURE 5 is a sectional elevation illustrating the stop mechanism and taken substantially on the line 5-5 as shown in FIGURE 4.

FIGURE 6 is a schematic elevation view similar to FIGURE 3 illustrating a modified form of apparatus for. the dual hydrofoil mechanism of this invention.

FIGURE 7 is a fragmentary sectional elevation View of the hydrofoil mounting taken substantially on the line 7-7 as shown in FIGURE 6.

FIGURE 8 is a fragmentary sectional view taken substantiallyffon the line see 7 lustrating the stop mechanism for this modified form of I similarto FIGURE 9 illustratingva change in the wind or 7 a tacking maneuvers when the wind is side as viewed in FIGURE 10. V a a Y 1 a g 7 FIGURE 11 is a schematic illustration similar'to FIG- URES 9 and 10 with a relatively v invention; 5

1 designated lthhas a center hull ll'and a pair of outrigger *lrulls 12" and 13 laterally spaced from and substantially parallel to center hull 11. The starboard and'port dutrig V "gers 12 and ll-respectively,Fare supported fromthe center a 7 hull 11 byanyconvenient means such by struts'15 andcertain ofthe structuralmemberst of the hydrofoil o --'mechanism, designated ,14, as Zhereinafter described. Struts 15 may also'serve as seating regions. A rudder 16 1 is pivotally mountedonithe ,stern'of hull ll and a tiller 1 Two hydrofoil assemblies,geneMllydesignated 26 the apparatus; a

I FIGURE 9 isa schematic illustration ofja trim aran' employing thedualhydrofoil ,rnechanism of m mention and is a head on view illustrating the positions of the hydrofoils 'when there is a veryitlight'wind from the right a side as viewed in FIGURE 9." a

' FIGURE'IO is atschematicillustration,ofa'trimaran V stiff wind fromthe left" side as viewed in FIGURE 11. i h 5 FIGURE 12 is a scheniatid illustration similar'to' 5181- i i forces are applied to the'trirnaran by the wind. e

FIGURE B is at'sectional plan View taken substantialgrammatically illustrates the asymmetrical-shape of the Although the'hdrawings illustrate the an hydrofoil mechanism of this invention as installed onthe outriggers t i of a trimaran sailboat, it is to be understood and will readily appear to those skilled in the art thatthejdualfhydro foil' mechanism 'may 'al'so'be' used on single or dou t, bIe hull sailboats. tVVhen' the o dual hydrofoilmechanism '7 of this invention is. used 'on'fa single hnll sailboat' ian ap V V t V propriatesu'uculremay be provided and extend outwardi 'lyfrom the hull lto supportrthe hydrofoilsin a manner similar to the hereinafter described structurei When dual hydrofoil mechanism of this invention is used ona as shown in FIGURE and il-i 7 h support tubes 21 and 22 with hydrofoil assembly 25 positioned in front of outrigger 12'andhydrofoil-assen1bly-27 '10 shifted to'the', left 7 'URES 9, 10' and ll showing' the trimaran either becalmed )Orrunning with the wind suchthat little or no lateral 7 1y on the line13-13 as shown in FIGURE 3 and dia-- J dual hull 6r catamaran s'ailboat, the hydrofoilsimay be 1 '7 mounted oneach of thehulls or onastru ctures exten zling' therefrom; Moreover, although the hydrofoils are shown inwardly .or outwardly from the outriggers by appropri- Referring now to the drawings, the tr imaran, generally mechanism 17 isprovided having fextensions 18 for ap v in'the drawings: astmounted on the :front portions of the a Outriggers of the catamaran, it will be 'appa'rentfrom the 7 following description that the hydrofoils could be spaced propriately operating the rudder 1515mm either of the r seating regions .onthe struts l d 'as is conventional. A

mast i9is providedfor supporting. sailsZtl inaconven tional manner. it

The frame of the hydrofoil mechanism 14 may include;

V a pair of: support tubes 21 and 22 extending latera ly 7 across hull 11 with each being mountedon hull 11' by a *pair of brackets 23. Bracketsl may also be provided on the extremities of support tube 22 for ,supporting the front end of the outrig'ger's'lz and 13. Appropriately locatedfwg'uy wires; suchas guy wires'25 extend fromthe outer ends ofsupporttubesll and 22 to the hull 11 and foil mechanism 14 and outriggers" 12 and 13. :Itiwill be;

type and 'style 'of sailboat employing the invention.

- mast'19 for aiding in 'the support and rigidity f the hydro- 1 tions' of operation. a

7 for mnning with the wind. The'wineh assemblyT32-is fpr L vided Wiihf a pairt of cordsl33, scured by[clamps 3410; cabIe SlQatspaced locations as shown; 1Uponfwinding 7 the cords'33onto the drum of the Winch'asseinblyfizj 'the cords- 33twil1 pull thetwoclamps 34'towardeachi othertherebyshortening the efiect'ive length of cablejfil and chang'ingthe 9Q relationshipbetweenthe two hydro-f1 toils .28. By tfo reshortening cable 31a'sufic'ienftarnount both hydrofoil members 28 may berais'ed' out "offthe water. In order to maintain the hydrofoilj28whichis inthe 5f water in the proper positionadepending'fonthe partieular "winds and force ,conditionsg means are provided folresiliently resisting movement, of either hydrofoil member'f j ZS'inan inward direction fromthe vertically downwardly 7 extending position suclitas that shown forchydr'o foil 2816139." ass'embly127 .iiiFIGUREj 3; Thesefmeans;may compris 1 a any v.eonvenierit:'type offresilient resistingi'apparatusIalR thoughI'pr'eferto use'and describe atorsionlmechanism generally designated '35, mountedin hull. 11. YTorsion in; I mechanismj r includesa torsion bar '37 rotatabl'y rnount H 1 L ed at one end, by a bearingtsupport- 38'ai1'd fixedlyinount- 1 ed at the other; end by support; 39,3 Torsion ibarrfaTniay we 7 be afiixed to supportf39 bya'ny conyenientrmeansl A to by any convenient means such as keyj41jQ'Sheavje is substantially spaced from Lthe endof torsion bar-57 -Wl1ich is afiixed in. supporti39 andis preferably near the 1 bearingsupp'o'rt A cable 42 e2rtenclsfrom thellowferl portion of sheave to :the upper; portion ofdrufm .29 of a the hydrofoil assemb1y '27and-ajsimilarxcable 43 extends from the upper portion of sheave 49 110" the drum'29 of hydrofoil assembly 'zor In the relative positions ofthe; various components shown in FIGURES}; 4 and 5,Ithe' V torsion bar 37 'is' in anjunstrcss'ed*Conglition, 'i,'e.,f' the torsion bar and sheave are 'intheirlneutral position. The cablefl42 is attached atone endito drum iigi'ata' location I 44 approximately diametrically spacedtfromthe attaeh 27, are. provided and 2mounted on thd-extrmitiesiofithe positioned in 'frontof outrigger 13; The-hydrofoil assem turn rotatably' mounted .on .a shaft 30 extending between and secured to support tubes at and}22. Altlidngh drumf 29is shown as a completecyl-inderjand such wouldp'robablybe the easiest rem toimmufacturmlitrwill readily V appear from the following description that drumf2 9'does a 7 not necessarily have to be a completecylinder andimore' 7 over could be oval. in cross-section. rather than cylindrical.

A line or cable SI eXtendsbetween the hydrofoil assent-t. blies 26 and 27 and isjsecured to thedrumportion29 of each byany convenient means in approximatelythe loca- 7 tions shown." The cable 3l is of a'parti cularlength'and 3 the ends are appropriately securedto 'drums .29,such that V i whentcablefil is stretchedtautly 'between'the hydrofoil 17 assemb1ies26 and 27 the hydrofoil 28 of'each assernblyfis' positioned at substantially 90fto thehydrofoil2$ of the V 7 other assembly when viewed fromthe fr'ontpr' rearQfThat fis'to sayf that when'hydrofoil- 28 of assembly 27 extends a vertically downward then hydrofoil l of assembly' 26;-

extends horizontally outward as'show'n in FIGURESfand i t'vice versa. Line 31 wraps around each'drum wanna-1- Q cient distance before attachmentito'theidrum so that this 90 relation hip maybemaint'ained; for all normal os' {A handt-operatedlwinch asseznbly'fiz dc mounted on the hull '11 for raising 159th of the ghydrofoils "1 zfi out ofthe'water when desired' such as for; dockingjori sheave 40 isjmounted on torsion bar 37 and secured there mentjof-hydrofoil 258. iiThep other" end oeab1ei42 is attached'tolsheave 4t onfthesideQof-the sheave opposite" f thefside of hydrofoil assembly 27 such as at location 45. j 7 Similarly, cable 43 is attaeh edlat location' lot'onfdrum z approximately diametrically'spaeed fromthy'dro foil 28 of a and assembly' z and the other end'of cable dll is attached 1 point 4-7 on sheave 49 on the opposite side of the sheave. Cable 42 will be taut when hydrofoil 28 of assembly 27 is extending vertically downward but torsion bar 37 will not be stressed, as shown in FIGURE 3. Likewise, cable 43 will be taut and torsion bar 37 unstressed when hydrofoil 28 of assembly 26 is extending vertically downward.

The specific functions served by the hydrofoils 28 will be more fully described hereinafter but at this point for purposes of description it will be assumed that during operation the leeward side hydrofoil assembly 26 or 27 will be positioned with the hydrofoil 28 projecting downwardly into the water and the various wind and water forces will tend to force that hydrofoil assembly to rotate about shaft 30 such that that hydrofoil 28 tends to pivot inwardly toward hull 11. In order for the hydrofoil mechanism of this invention to perform the functions desired this inward movement must be resisted. Referring specifically to FIGURE 3, it will be assumed that outrigger 13 and hydrofoil assembly 27 are on the leeward side and ince the wind is coming from the left the hydrofoil 28 of that assembly is being urged toward the left or inwardly thus tending to rotate the drum 29 of that assembly in a clockwise direction. Any clockwise rotation of drum 29 of assembly 27 will tend to wrap additional cable 42 onto that drum and since cable 42 is taut when hydrofoil 28 of assembly 27 is projecting vertically down ward, the wrapping of cable 42 on the drum will tend to pull the cable off sheave 44 thereby causing sheave 40 to rotate in a counterclockwise direction as viewed in FEGURE 3. Since sheave 40 is secured to torsion bar 37 which is in turn secured .to support 39, this rotation of sheave 453 will be resiliently resisted by the torsion stresses induced in the torsion bar 37. The greater the inward angular displacement from vertical of hydrofoil 28 the greater will be the resilient torsion resistance by torsion bar 37. his also to be noted that this inward movement of hydrofoil 28 of assembly 27 causes raising of hydrofoil 2-8 of assembly 26 above the horizontal due to the interconnection by cable 31.

Similarly, it may be seen that when hydrofoil assembly 26 is on the leeward side and that hydrofoil 28 is in a vertically downward projecting position cable 43 will be taut and inward movement of hydrofoil 28 from that position causes counterclockwise rotation of the drum 29 of that assembly thereby wrapping cable 43 onto that drum and unwrapping some of that cable from sheave 49. This causes sheave 49 to rotate in a counterclockwise direction. As previously described, this counterclockwise rotation of sheave 44) is resiliently resisted by torsion bar 37. It is to be noted that sheave 40 is rotated in a counterclockwise direction by the movement of hydrofoil 28 of either of the hydrofoil assemblies 26 or 27 inwardly from the vertical downwardly extending position. For reasons that will hereinafter become apparent it may be desirable to limit the extent of inward angular displacement from the vertically downward position of the hydrofoil 28 which may be permitted regardless of the wind and water forces and such may be accomplished by providing a stop means on torsion bar 37. This stop means may include stops 4% on torsion bar 37 near sheave 4i projecting radially outwardly and adapted to engage similar stops 49 secured to the bearing support 38. Thus, as shown in FIGURE 5, the angular displacement of torsion bar 37 and sheave 49 is limited to approximately 45 and if sheave 40 and drums 29' are approximately the same diameter as shown, the angular displacement of either of the hydrofoil members 28 will be limited to 45 from the downward vertical position. This limitation of 45 is meant only as illustrative and inactual practice may be varied for various types and styles of sailboats and to obtain various operating characteristics.

Referring now more particularly to FIGURES '6, 7 and 8, a modified form of apparatus is shown for the dual hydrofoil mechanism of this invention. In this form, the need for the torsion mechanism 36 installed in 6 hull 11 and cables 42 and 43, as previously described,

is eliminated. Hydrofoil assemblies, generally designated 53 and 51, are provided similar to the provision of hydrofoil assemblies 26 and 27. The frame work structure for supporting the outrigger hulls 12 and 13 and the hydrofoil assemblies 59 and 51 from the center hull 11 may be substantially the same or similar to that previously described. The hydrofoil assemblies 51' and 51 are each comprised of a hydrofoil 52 mounted on a sheave 53 similar respectively to hydrofoil 28 and drum 29 previously described. Sheave 53 and hydrofoil 52 are affixedly mounted to a torsion shaft 54 by any convenient means such as key 55. Torsion shaft 54 is rotatably mounted and supported by bearings 55 on either side of the hydrofoil 52. Torsion shaft 54 is relatively long and extends rearwardly into the associated outrigger hull being rotatably supported near the rearward end by bearing support 57 mounted in the outrigger hull. A splined stop member 58 is mounted on the end of torsion shaft 54 and has a stop arm 59. Stop arm 59 is adapted to engage a stop 60 secured to the bearing support 57, such that inward movement of hydrofoil 52 from the vertically downward projecting position is prevented unless sulficient force is applied to twist the torsion shaft 54. Thus, it may be seen that the separate torsion shafts 54 of this modified form serve the same function as the torsion assembly 3d and connecting cables 42 and 43 heretofore described since inward movement of either hydrofoil member 52 beyond the downward vertical position is resiliently resisted by a torsion bar. The outward and upward movement of each hydrofoil member 52 from the downward vertical position is unimpeded since stop arm 59 only engages one side of stop 6% and is free to move in the other direction. A cable 61 is provided similar to cable 31 and is appropriately connected to the sheaves 53 of the hydrofoil assemblies Stl and 51 so that the hy-' drofoils 52 of those two assemblies aremaintained at with respect to each other at all times in the same manner as heretofore described.

Each of the hydrofoil members 28 or 52 are relatively long and have an asymmetrical shape as may be seen by the cross-section shown in FIGURE 13. One side n2 is relatively fiat while the other side 63 is curved out wardly and tapered to form a relatively conventional hydrofoil shape. When the particular hydrofoil member extends downwardly in the vertical position the flat side 62 faces outwardly from the center of the boat and the curved side 63 faces inwardly. As is well known in the art, a hydrofoil of such configuration passing through the water with the flat side 52 coinciding with the direction of movement will produce a force on the hydrofoil tending to move the hydrofoil in the direction of the curved side 63. Thus, whatever the hydrofoil is attached to would tend -to move with the hydrofoil in the direction of the curved side. Moreover, if a hydrofoil is positioned horizontally with the curved side facing upwardly, the hydrofoil will produce a lifting force.

Referring now more particularly to FIGURES 9 through 12, the operation of the dual hydrofoil mechanism of this invention may be described in relation to the response of the mechanism to various wind conditions. As heretofore described, FIGURES 9, 10, 11 and 12 will be assumed to be headon views of the trimaran it previously described and, therefore, port will be to the right and starboard to the left as viewed in these figures. The dual hydrofoil mechanism may be either the type shown in FIGURES 1 through 5 or the type shown in FIGURES 6 through 8 and the operation will be identical although for purposes of description here it will be assumed that the mechanism of FIGURES 1 through 5 is being used. If the sailboat is completely becalmed and motionless the hydrofoils 28 would probably be in a position shown by the solid lines in FIGURE 12 where each hydrofoil projects downwardly and outwardly into the water at approximately 45 to the water line. It is again to be noted that the hydrofoils are maintained at approximately 90 with J lt'is preferred in the particular embodiment of this t invention in a trimaran that theoutrig'ger hulls 12 and 13 to move toward leeward, i.e., starboard and the relative '1 .rn ovement between the sailboat and the water would cause the starboard hydrofoil 28 to be pulled downwardly to.

the'vertical positions-shown in FIGURE 9 thereby-raising the port or windwardside hydrofoil 23 out of the water.

- This position is also shown by the dashedlines 'in FIG-' V 'URE 10. However, a shift in the wind or 'tacking so'that the wind impinges on the starboard side, as shown in FIG- the starboard hydrofoil 28 since outward pivoting motion l 10 URE 10, will cause the trimaran 10 to moveto port relative to the water and this motion will not beresisted by is unimpeded; As soon as starboard hydrofoil 28 moves 1 outwardly and upwardly the port hydrofoil 28 drops into the water and further port movement of the sailboat causes a that hydrofoil to assume the vertical downwardly project: ing position shown by the solid lines in FIGURE 10. Increased wind from starboard. such as changes inwind conditions or changes indirection with respect'tothe direc.-' tion' of: the'wind will'cause' increased overturnn'ag'forces on the sailboat and increased fo'rcesftendirigto make the sailboat -slip laterally rather than proceeding directly 7 ahead as controlled by rudder 16.. The lateral forces-from. starboard will be resisted'by the port hydrofoil member" 28 since thathydrofoil is extending downwardly into the 7 ,Water and the lateral forces. will cause that hydrofoilto "pivot inwardly ,towardthe central 'hull'll' thereby assuming a condition which maybe represented byFIGURE 11. The angular portion of the hydrofoil wiil depend 'upon the intensity of the lateral forces being resisted, and it may readily be seen that the greater the lateral, force the more the'ihydrofoilwill extend inwardly-rather than -dow n-' 'Wardly. i

Turning now'to the function of the asymmetrical shape of the hydrofoils, it maybe seen that if the sailboat is moving straight through. the water with the leeward side hydrofoil extending vertically, downwardly 'thattherewill be a resultant force; produced'by the hydrofoiltending tomov e the sailboat toward windward since the curved side will. be facing windward; 7 As the hydrofoiltass'umes an angular position Qs uchas that shown for theport-hydroa foil inemberin FIGURE 11 the force produced'by' thev hydrofoil passing, through the waterwill have both a horizontal component anda verticalfcomponent. The horizontal component 'is still directed toward Windward to resist side slipping of the sailboat and the vertical force component is upwardly to, in reffectjsupport some of the \veight of, the sailboat. Since this'vertical lifting com ponent offorce is laterallyspjaced fromi'thecenter of gravity "of" the sailboat a forcemoment is. produced in :1

opposition to'the overturning force 'momentrproduced by the wind impingingon'thesails; As is {well known, a b V hydrofoil depends upon'its shapefor' producinglifting forcesland the lifting forc'esproduced when the hydrofoil is passing through the water greatly exceeds'the I buoyancy of the hydrofoil. Thus,'as shown in FIGURE 7 j 11', a largeportion of the weight of the sailboat may be supportedbythe leeward side hydrofoil member 28 and as a consequence the center hull 11 may lift nearly free of the water or at least to a position where it is planing. 7 :along the surface of the water. the resistive drag of the center hull is greatly reduced and Under suchconditions,

performance characteristics a'regreatly improved; More-.

'over,jit may 'be seen that 'the greater the lateral wind leeward hydrofoil member-since the increased lateral force causes the hydrofoil member to more closely apforces the greater will be the lifting forceproduced by the '6 preach a horizontal position than the verticalrposition.

be positionedabove the water when in a level position Further, the bottom surfacesof outrigger hulls 12 and l3 and that the entire weight be, supportedby hull 11 1 changes in wind 30 an angle to the horizontal SiCll V V the trimaran it} to heel over, as shown in FEGURESIO merely operating winch V scribed, to foreshorten cable 31,-.

- Thus, it maybe seen thatjby this invention there-is Q provided a hydrofoil mechanism for sailboatswhich 'funt tions' without attention to position a hydrofoilin the; water always on' the leeward side of the sailboat -withthe angular position of the hydrofoil being automatically ad; I V .iu sted in response to the conditionsoflateralforiceim posedupon-the sailboat. lt lore'over, by employing dualf asymmetrically shaped hydrofoils which are automati 3 cally andproperlyoriented a-highly desirable'lifting force is produced'on-the leeward side of the sailboat' to' resist overturning and improve operatingcharacteristics. ;'Furthen; this: lifting force "results" in a portion orfall of the 3 hull being lifted out'df the water to thereby minimize the 25 water drag produced by the hu'llj Eachlof'the'seiunusml functions are accomplished automatically by the ,apparatus of this invention and such: apparatus does notrequire i; :attention during; normalisailing'for compensating: for Conditions; direction or movemenLjtacking, etc.

7 Having fully described my inventionlit'is 'to'beunderstood that I doinot wish to be' limited to the details herei? in set forth or to the detailsiillustrated 'in. the drawings; but my inventionis offthe. full. scope or the "appended 1;

claims; V I claim 1. An apparatus for asailboat comprising, aLPairfhydrofoils ivotaHY-mosmed came amanat laterally spaced locations 'ori eithlersideof the longitudinal'center 1 i' line of the sailboat, said hydrofoils having ran asymmetri 1 cal shape for' -producinga lateral foroe'whenipassing through the'water, means for automatically piyotin'g each:

Y 'ofsaid hydrofoils solely in response to winfd impinging" onrthe sailboat to. raise the windward side hydrofoil out I or the water and to lower theleeward side hydrofoilinto the watergmeansifor further pi oting said leeward side 1 hydrofoil in response to: wind-forces to angularlyposi- 7 tio'n that'hydrofoil in the water such that'thl said lateral- Q force produced by said asymmetrical. shape resists-both sideways slipping and overturning,forcesfimposedon the.

sailboat by the wind.

2'. An apparatus for a sailboat com'prising, when f hydrofoils, each hydrofoil; being asymmetricalj'with one side curved and the am nds relatively flatQoneQof said hydrofoilspositioned on either side ofand laterally spaced a substantial distance fromgthe longitudinal center linej, F of said heat, each' said hydrofoilipivotallygmounted.byi. one end on the; sailboat'on an aris relatively parallel 'to the'longitudinalcenter line of the sailboat and llocatecl 7 above the. normalwater line of the 'sailboatfor said 'hydrofoil to engage thewater when extending downwardly; i

7 each of said hydrofoils oriented such that said flatside a faces outwardly from the sailboat when that hydrofoil ex Y tends downwardly from. the" pivotal mounting thereof, 1 means operably. connecting the :two' said hydrofoilsfor, asynchronous movement of said hydrofoilsl forpivoting .one hydrofoil out of the water when as other hydrofoil; is in thewater in downwardlyand downwardly-inw ardly-l extending positions, meansresisting' pivoting of either said hydrofoil in an inwardly direction from news;

'cally' downward both hydrofoils boat extending position "of such hydrofoil,

wind I impinging on the sailboat with theileeward side's hythat whenthe wind causes V extending into the waterwhen the gail-l'. i 1s stopped or. moving with the'win'd, meairs 1for auto-'s a l natically p yoting said hydrofoilssolely in response'rto drofoil assuming a downward and relatively vertical position to resist the lateral motion of the sailboat.

3. An apparatus for a sailboat comprising, a pair of hydrofoils, each hydrofoil being asymmetrical with one side curved and the other side relatively flat, one of said hydrofoils positioned on either side of and laterally spaced a substantial distancefrom the longitudinal center line of the said boat, each said hydrofoil pivotally mounted by one end on the sailboat on an axis relatively parallel to the longitudinal center line of the sailboat and located above the normal water line of the sailboat for said hydrofoil to engage the water when extending downwardly, each of said hydrofoils oriented such that said fiat side faces outwardly from the sailboat when that hydrofoil extends downwardly from the pivotal mounting thereof, means operably connecting the two said hydrofoils for synchronous movement of said hydrofoils for pivoting one hydrofoil out of the water when one other hydrofoil is in the water in downwardly and downwardly-inwardly extending positions, means resiliently and increasingly resisting pivoting of either said hydrofoil in an inwardly direction toward the center line of the sailboat from the vertically downward extending position of such hydrofoil; both hydrofoils extending into the water when the sailboat is stopped or moving straight forward, upon wind impinging on the sailboat to produce lateral forces urging lateral motion the leeward side hydrofoil assuming a downward and relatively vertical position to resist the lateral motion, and increasing lateral force causing said leeward side hydrofoil to pivot inwardly in opposition to said resisting means for producing an upward lifting force by that hydrofoil due to the asymmetrical shape.

4. An apparatus for a sailboat comprising, a pair of hydrofoils, each hydrofoil being asymmetrical with one side curved and the other side relatively flat, one of said hydrofoils positioned on either side of and laterally spaced a substantial distance from the longitudinal center line of the said boat, a sheave means connected to each hydrofoil at one end, each said hydrofoil and sheave means pivotally mounted on the sailboat by said sheave means on an axis relatively parallel to the longitudinal center line of the sailboat and located above the normal water line of the sailboat for said hydrofoil to engage the water when extending downwardly, each of said hydrofoils oriented such that said flat side faces outwardly from the sailboat when the hydrofoil extends downwardly from the pivotal mounting thereof, cable means extending between the two said sheaves and connecting thereto for causing synchronous movement of said hydrofoils for pivoting one hydrofoil out of the water when the other hydrofoil is in the water in downwardly and downwardlyinwardly extending positions, means resiliently and increasingly resisting pivoting of either said hydrofoil in an inwardly direction toward the center line of the sailboat from the vertically downward extending position of such hydrofoil; both hydrofoils extending into the water when the sailboat is stopped or moving straight forward, upon wind impinging on the sailboat to produce lateral forces urging lateral motion the leeward side hydrofoil assuming a downward and relatively vertical position to resist the lateral motion and increasing lateral force causing said leeward side hydrofoil to pivot inwardly in opposition to said resisting means for producing an upward lifting force by that hydrofoil due to the asymmetrical shape.

5. An apparatus for a sailboat comprising, a pair of hydrofoils, each hydrofoil being asymmetrical with one side curved and the other side relatively flat, one of said hydrofoils positioned on either side of and laterally spaced a substantial distance from the longitudinal center line of the said boat, each said hydrofoil pivotally mounted by one end on the sailboat on an axis relatively parallel to the longitudinal center line of the sailboat and located above the normal water line of the sailboat for said hydrofoil to engage the water when extending downwardly, each of said hydrofoils oriented such that said flat side faces outwardly from the sailboat when that hydrofoil extends downwardly from the pivotal mounting thereof, means operably connecting the two said hydrofoils for synchronous movement of said hydrofoils for pivoting one hydrofoil out of the water when the other hydrofoils is in the water in downwardly and downwardly-inwardly extending positions, torsion bar means mounted in the sail boat and operatively connected to both said hydrofoils for resisting pivoting of said hydrofoils inwardly from the vertically downward extending position and permitting pivoting of said hydrofoils outwardly from the vertically downward extending position; both hydrofoils extending into the water when the sailboat is stopped or moving straight forward, upon wind impinging on the sailboat to produce lateral forces urging lateral motion the leeward side hydrofoil assuming a downward and relatively vertical position to resist the lateral motion and increasing lateral force causing said leeward side hydrofoil to pivot inwardly in opposition to said torsion bar means for producing an upward lifting force by that hydrofoil due to the asymmetrical shape.

6. An apparatus for a sailboat comprising, a pair of hydrofoils, each hydrofoil being asymmetrical with one side curved and the other side relatively flat, one of said hydrofoils positioned on either side of and laterally spaced a substantial distance from the longitudinal center line of the said boat, each said hydrofoil pivotally mounted by one end on the sailboat on an axis relatively parallel to the longitudinal center line of the sailboat and located above the normal water line of the sailboat for said hydrofoil to engage the water when extending downwardly, each of said hydrofoils oriented such that said flat side faces outwardly from the sailboat when that hydrofoil extends downwardly from the pivotal mounting thereof, means operably connecting the two said hydrofoils for synchronous movement of said hydrofoils for pivoting one hydrofoil out of the water when the other hydrofoil is in the water in downwardly and downwardly-inward- 1y extending positions, a torsion bar mounted in the sailboat, a sheave mounted on said torsion bar, cable means connecting said sheave to each said hydrofoil for causing turning of said sheave upon pivoting of either said hydro- 'foil in an inwardly direction toward the center line of the sailboat from the vertically downward extending position of such hydrofoil, said turning of the sheave being resiliently resisted by said torsion bar, and the magnitude of such resilient resistance by said torsion bar being proportional to the magnitude of the inward angular displacement of a hydrofoil from the vertical downwardly extending position.

7. An apparatus for a sailboat comprising, a pair of torsion shafts mounted on the sailboat relatively parallel to the longitudinal center line of the sailboat and laterally spaced from such center line, one torsion shaft on either side of such center line and above the normal water line of the sailboat, each torsion shaft having one end freely rotatably supported and the other end turnably supported with means for stopping the turning at a predetermined location, a hydrofoil mounted on each said torsion shaft near the first-mentioned end and extending outwardly from said torsion shaft, each hydrofoil being asymmetrical with one side curved and the other side relatively flat, each of said hydrofoils oriented such that said flat side faces outwardly from the sailboat when that hydrofoil extends downwardly from said torsion shaft, means operably connecting the two said hydrofoils from synchronous movement of said hydrofoils for pivoting one hydrofoil out of the water when the other hydrofoil is in the water in downwardly and downwardly-inwardly extending positions, the said means for stopping turning of each said torsion shaft permitting free outwardly and upwardly movement of that said hydrofoil from the vertical downwardly extending position and stopping said torsion shaft for resiliently resisting inward movement r, r 7' 7121' r 7 References Cited by th evExa'minelv I UNITEDYSTATES A ENTS:

. V V FOREIGN- PATENTS 2s2,10s**7/'2 s "Great Britain; 1,063,731 I 1.2/53 France.

'19 FERGUS s.- MIDDLETON, Primdfy' Erzz i'nrg 

1. AN APPARATUS FOR A SAILBOAT, COMPRISING, A PAIR OF HYDROFOILS PIVOTALLY MOUNTED ON THE SAILBOAT AT LATERALLY SPACED LOCATIONS ON EITHER SIDE OF THE LONGITUDINAL CENTER LINE OF THE SAILBOAT, SAID HYDROFOILS HAVING ASYMMETRICAL SHAPE FOR PRODUCING A LATERAL FORCE WHEN PASSING THROUGH THE WATER, MEANS FOR AUTOMATICALLY PIVOTING EACH OF SAID HYDROFOILS SOLELY IN RESPONSE TO WIND IMPINGING ON THE SAILBOAT TO RAISE THE WINDWARD SIDE HYDROFOIL OUT OF THE WATER AND TO LOWER THE LEEWARD SIDE HYDROFOIL INTO THE WATER, MEANS FOR FURTHER PIVOTING SAID LEEWARD SIDE HYDROFOIL IN RESPONSE TO WIND FORCES TO ANGULARLY POSITION THAT HYDROFOIL IN THE WATER SUCH THAT THEM SAID LATERAL FORCE PRODUCED BY SAID ASYMMETRICAL SHAPE RESISTS BOTH SIDEWAYS SLIPPING AND OVERTURNING FORCES IMPOSED ON THE SAILBOAT BY THE WIND. 